This invention relates to a connection arrangement for electronic equipment to provide functional expansion in at least one dimension.
Electronic equipment is frequently constructed in modular fashion in a rack on the basis of standard rack units, which are 21 inches (53.34 cm) wide and 1.75 inches (4.45 cm) high. A given rack might accommodate multiple modules stacked one above the other. A module typically includes a vertically disposed mother board carrying multiple vertically disposed edge connectors into each of which a vertically disposed daughter board can be plugged in perpendicular relationship with the mother board. In some types of equipment the daughter boards are all identical and each daughter board can be characterized as having a capacity n in a first dimension, which may be arbitrarily labeled the X dimension, and a capacity m in a second, or Y, dimension. Each module contains the same number N of daughter boards.
The capacity of the equipment in the X dimension is determined by the capacity of the daughter boards in the X dimension and the number of daughter boards in each module and is typically n*N. The capacity of the equipment in the Y dimension is determined by the capacity of the daughter boards and the number of modules in the equipment and if there are M modules, the capacity is typically m*M.
In electronic equipment that can be characterized in this manner as having capacity in two orthogonal dimensions, it may be desirable to have the ability to expand the equipment in one or both dimensions. Expansion in the X dimension can be accommodated by adding a daughter board to each module, increasing the capacity to n*(N+1) whereas expansion in the Y dimension to m*(M+1) can be accommodated by adding a module including N daughter boards.
When equipment of this nature is expanded in the Y dimension, it may be necessary to connect each daughter board of the added module to the corresponding daughter board of at least one adjacent module; and when the equipment is expanded in the X dimension, it may be necessary for each daughter board that is added to a module to be connected to the corresponding daughter board that is added to at least one adjacent module. It may also be necessary to disconnect the daughter board of one module from the corresponding daughter board of an adjacent module when the daughter board is removed, for example for replacement.
In an arrangement disclosed in U.S. Pat. No. 5,205,753 (Butterfield et al), connection or disconnection of corresponding daughter boards is accomplished by use of a cam mechanism which can be actuated when a daughter board is inserted into the module. By actuation of the cam mechanism, a female connector part carried by the daughter board is displaced vertically and engages a complementary male connector part of the corresponding daughter board in an adjacent module.
The circuit board structure shown in Butterfield et al is subject to disadvantage because it employs several moving parts and is therefore rather expensive to manufacture to the standard necessary for trouble-free operation.
It is conventional to locate a circuit board in a mounting structure by reference to routed edges of the board. However, routing of circuit board edges is not a high precision operation and an error in routing can result in an error in positioning of the board relative to its mounting structure. Conversely, it is possible to drill holes in a workpiece at precisely controlled relative positions.